Lecture of the Week: Why are We So Smart?
- From: "Wirt Atmar" <atmar@xxxxxxxxxxxxxxxxx>
- Date: Tue, 19 Sep 2006 13:40:38 -0400 (EDT)
The Evolutionary Biology Lecture of the Week for September 18, 2006 is
now available at:
http://aics-research.com/lotw/
The talks center primarily around evolutionary biology, in all of its
aspects: cosmology, astronomy, planetology, geology, astrobiology,
ecology, ethology, biogeography, phylogenetics and evolutionary biology
itself, and are presented at a professional level, that of one
scientist talking to another. All of the talks were recorded live at
conferences.
=====================================
September 18, 2006
Part II: What Makes Us Human?
The Origin of Adaptability and Human Beings
Rick Potts
Smithsonian Instituition
35 min.
"Man's structural peculiarities only suffice to place him in a
monotypic zoological family, with a single living species. His mental
abilities are far more distinctive. If the zoological classification
were based on psychological instead of mainly morphological traits, man
would have to be considered a separate phylum or even kingdom."
- Theodosius Dobzhansky (1900 - 1975)
Species are often ecologically classified as adopting either an
r-selected or K-selected strategy, where "r" is the instrinic rate of
increase of the species and "K" is the carrying capacity of the
environment.
An r-selected species is at its most competitive when it is invading
disturbed habitat. It temporarily prospers because it can increase its
numbers faster than any of its competitors, but such a strategy will
eventually normally lose out to species that are more competitive once
the resource space fills, should it remain stable.
R-selected species are often called "weed species" because they depend
so heavily on disturbed habitat. Although Rick Potts never uses the
term in this talk on the evolution of humans, that is the organism he
is describing. Humans are now the sole surviving hominid species on the
planet, but that wasn't true until quite recently.* From his work in
his Turkana Basin and Olorgesailie sites in East Africa, as well as his
more recent work in southern China, Potts outlines a compelling
argument that Homo evolved to prosper best during periods of climatic
instability.
Climatic instability affects all species. Generally, only three choices
are offered a species:
o extinction in face of the changed environment
o migration to more clement environments
o adaptation to the broader range of environments
The genus Homo evolved - perhaps only by chance and not too much
should be made of the fact - during a period of dramatically
increasing climatic instability. Potts argues however that the recent
increases in climatic oscillations lie at the core of the evolution of
Homo.
While the increases in climatic variation appear in the fossil record
to have suppressed populations of the more inertial hominins,
Paranthropus and Australopithecus, the increased environmental stress
apparently acted as an "intelligence pump" in Homo, forcing the lineage
to become more inventive in its responses to a broader range of
inclement environments.
In that, Potts' argument not only goes a long way in answering the
question, "Why are we so smart?", it also recapitulates the "complexity
pump" thesis that Andrew Knoll argued in an earlier lecture: evolution
on a stable planetary surface would soon come to an end without
episodic disturbances. Some degree of instability is necessary to cause
life to become increasingly more complex.
Rick Potts presented his talk at an astrobiology conference, thus the
question at the end was whether or not this level of instability is
universally requisite to the evolution of intelligence elsewhere in the
galaxy? Potts argues yes.
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